java_cup.symbol Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of javacup Show documentation
A fork of the Java Cup parser generator with some bug fixes and enhancements. (Forked at version 11b)
The newest version!
package java_cup;

/**
 * This abstract class serves as the base class for grammar symbols (i.e.,
 * both terminals and non-terminals).  Each symbol has a name string, and
 * a string giving the type of object that the symbol will be represented by
 * on the runtime parse stack.  In addition, each symbol maintains a use count
 * in order to detect symbols that are declared but never used, and an index
 * number that indicates where it appears in parse tables (index numbers are
 * unique within terminals or non terminals, but not across both).
 *
 * @author Frank Flannery
 * @version last updated: 7/3/96
 * @see java_cup.terminal
 * @see java_cup.non_terminal
 */
public abstract class symbol {
   /*-----------------------------------------------------------*/
   /*--- Constructor(s) ----------------------------------------*/
   /*-----------------------------------------------------------*/

    /**
     * Full constructor.
     *
     * @param nm the name of the symbol.
     * @param tp a string with the type name.
     */
    public symbol(String nm, String tp) {
       /* sanity check */
        if (nm == null) nm = "";

       /* apply default if no type given */
        if (tp == null) tp = "Object";

        _name = nm;
        _stack_type = tp;
    }

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /**
     * Constructor with default type.
     *
     * @param nm the name of the symbol.
     */
    public symbol(String nm) {
        this(nm, null);
    }

   /*-----------------------------------------------------------*/
   /*--- (Access to) Instance Variables ------------------------*/
   /*-----------------------------------------------------------*/

    /**
     * String for the human readable name of the symbol.
     */
    protected String _name;

    /**
     * String for the human readable name of the symbol.
     */
    public String name() {
        return _name;
    }

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /**
     * String for the type of object used for the symbol on the parse stack.
     */
    protected String _stack_type;

    /**
     * String for the type of object used for the symbol on the parse stack.
     */
    public String stack_type() {
        return _stack_type;
    }

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /**
     * Count of how many times the symbol appears in productions.
     */
    protected int _use_count = 0;

    /**
     * Count of how many times the symbol appears in productions.
     */
    public int use_count() {
        return _use_count;
    }

    /**
     * Increment the use count.
     */
    public void note_use() {
        _use_count++;
    }
 
  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /**
     * Index of this symbol (terminal or non terminal) in the parse tables.
     * Note: indexes are unique among terminals and unique among non terminals,
     * however, a terminal may have the same index as a non-terminal, etc.
     */
    protected int _index;

    /**
     * Index of this symbol (terminal or non terminal) in the parse tables.
     * Note: indexes are unique among terminals and unique among non terminals,
     * however, a terminal may have the same index as a non-terminal, etc.
     */
    public int index() {
        return _index;
    }

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /**
     * Indicate if this is a non-terminal.  Here in the base class we
     * don't know, so this is abstract.
     */
    public abstract boolean is_non_term();

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /**
     * Convert to a string.
     */
    public String toString() {
        return name();
    }

  /*-----------------------------------------------------------*/

}